The present invention relates to the field of fertilizer compositions and, more particularly, to a thixotropic fertilizer suitable for application simultaneously with planting an agricultural crop.
Plant fertilizers have been used from earliest human efforts at agriculture. The simplest and most readily accessible fertilizers in many parts of the world have been animal manure, and even human wastes. Chemical fertilizer compositions have been developed for providing more selective and controlled delivery of nutrients and to avoid the well known public health problems associated with use of animal and human waste as fertilizers.
Thixotropy refers to a property of certain materials for forming a gel when undisturbed and becoming fluid when disturbed, such as by shaking or mixing. A thixotropic composition is one which is a gel when at rest, and which becomes liquid when agitated. The property of thixotropy has been previously employed in manufacturing animal feeds and fertilizers. However, in the fertilizer field, thixotropy has been largely perceived as an undesirable characteristic causing unwelcome destruction of suspension fluidity during storage of fertilizer compositions. In this regard, for example, see U.S. Pat. No. 5,022,913, issued to Dillard et al., and describing how to make a stabilized ammonium orthophosphate suspension while avoiding such undesirable gelling.. Gels have also been prepared in dry form for application to the soil, for example, as described in U.S. Pat. No. 5,632,799, issued to Behel et al. on May 27, 1997. A hydrogel formed with crosslinked polyacrylamide has been described in U.S. Pat. No. 5,221,313 by Mortvedt for use as a fertilizer. However, Mortvedt provides a different chemical formulation, necessarily having different properties from the composition herein, and in addition Mortvedt does not suggest a thixotropic gel fertilizer wherein the gel is formed essentially as the fertilizer is being applied. Instead, Mortvedt applies its fertilizer as a preformed gel, admitting that such hydrated gels are rather difficult to apply and that their relatively high cost of application limits their utility to specialty crops such as apples, grapes, and peaches. Mortvedt points out the utility of an economically viable method of application for field crops such as soybeans and grain sorghum. The present invention advantageously describes such a method.
With the foregoing in mind, the present invention advantageously provides a thixotropic fertilizer composition including a first aqueous component having predetermined concentrations of divalent cations and organic matter, and a second aqueous component having a predetermined concentration of phosphorus and having substantially no divalent cations, wherein the first and second aqueous components are mixed in predetermined proportions to produce the thixotropic fertilizer composition substantially having concentrations of divalent cations of about 1% by weight, of about 25% by weight of dry organic matter, and of about 1% by weight of phosphorus.
The present invention includes an apparatus for applying the thixotropic fertilizer composition. The apparatus includes a plurality of containers, each container of the plurality for containing each liquid component, to thereby keep the liquid components separate from each other. The apparatus further includes a plurality of conduits, each conduit having a first end and a second end, the first end being connected in fluid communication with a container of the plurality of containers for conducting the liquid component therefrom. A mixing chamber is positioned downstream from the plurality of conduits, the second end of each conduit of the plurality being connected in fluid communication with the mixing chamber for conducting thereinto the plurality of liquid components for mixing. A pump is connected in fluid communication with the plurality of containers for pumping the plurality of liquid components through the apparatus. A nozzle is connected in fluid communication with the mixing chamber and is positioned downstream therefrom for delivering the thixotropic fertilizer composition to the soil after mixing, thereby fertilizing the soil.
The invention additionally describes a method of fertilizing an agricultural crop, the method including the step of applying a thixotropic fertilizer substantially simultaneously with planting the agricultural crop. Preferably, the thixotropic fertilizer is applied to the soil essentially under the soil surface, so that when the crop being planted is covered with soil the fertilizer also covered. Additionally included in the invention is a method of making a thixotropic fertilizer, including the steps of: preparing a first aqueous component having predetermined concentrations of divalent cations, and organic matter; preparing a second aqueous component including a predetermined concentration of phosphorus, and substantially no divalent cation; and mixing the first and second aqueous components in predetermined proportions to produce a thixotropic fertilizer composition substantially having concentrations of divalent cations of about 1% by weight, of about 25% by weight of dry organic matter, and of about 1% by weight of phosphorus.